(1) Field of the Invention
This invention relates to couplings for articulated wheeled land vehicles, and more particularly to draft pins for such couplings.
(2) Description of the Prior Art
Draft pins are commonly used to couple a towing vehicle hitch and a towed vehicle tongue with holes therein. However, a recurring problem is how to prevent friction and vibration from working the pin up out of the holes, resulting in the disconnection of the towing and towed vehicles with possibly disastrous results.
Previously, one solution to this problem was loosely attaching a C-shaped member to a draft pin, the lower end of which swung by gravity below the hitch members and prevented the draft pin from rising above the lower end of the C-shaped member.
Other workers in the art did not desire to rely upon gravity to maintain the C-shaped member in a proper position. Therefore, these other workers developed means for locking the retaining member in place.
Many of the trailer couplers of the prior art required the use of two hands to lock and unlock them, and often involved intricate, delicate mechanisms for ther performance. In addition, many such devices did not provide a means for holding the retaining handle in an unlocked position.
NEUMANN, U.S. Pat. No. 3,011,801, uses an eyelet formed in the lower end of the C-shaped retaining member which slides over the end of the draft pin and is kept in a position above the lower end of the draft pin by spring means at the top of the draft pin and retaining member.
JEZEK, U.S. Pat. No. 3,196,239, keeps the C-shaped retaining member in position in a similar way, but in addition provides a plate which prevents the retaining member from being pushed down unless the other side of the plate is depressed also.
KELLOG ET AL, U.S. Pat. No. 2,547,326, uses an engaging pin connected to the C-shaped retaining member to positively engage a hole in a pivoting draft pin to keep the retaining member in position relative to the draft pin. The C-shaped retaining member is unlocked by pulling the engaging pin from the hole in the draft pin.
The following patents were known to me at the time of filing this application:
Backman -- 2,786,383 PA0 Bible -- 2,454,856 PA0 Kelley -- 2,367,874 PA0 Rebaylio -- 2,303,260 PA0 Peterson -- 2,224,522 PA0 Stastny -- 2,180,558 PA0 Davidson -- 2,007,825